U.S. patent number 4,286,881 [Application Number 06/015,397] was granted by the patent office on 1981-09-01 for sample cell.
This patent grant is currently assigned to Phillips Petroleum Company. Invention is credited to Jay Janzen.
United States Patent |
4,286,881 |
Janzen |
September 1, 1981 |
Sample cell
Abstract
A sample cell with at least one movable lens is provided for
spectrophotometric study.
Inventors: |
Janzen; Jay (Bartlesville,
OK) |
Assignee: |
Phillips Petroleum Company
(Bartlesville, OK)
|
Family
ID: |
21771169 |
Appl.
No.: |
06/015,397 |
Filed: |
February 26, 1979 |
Current U.S.
Class: |
356/440;
352/244 |
Current CPC
Class: |
G01N
21/03 (20130101); G01N 21/0303 (20130101) |
Current International
Class: |
G01N
21/03 (20060101); G01N 021/01 () |
Field of
Search: |
;356/244,409,432,436,440,442 ;250/227 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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|
|
|
|
|
1959612 |
|
Jun 1971 |
|
DE |
|
2133797 |
|
Jan 1973 |
|
DE |
|
2272378 |
|
Dec 1975 |
|
FR |
|
Primary Examiner: Rosenberger; R. A.
Claims
What is claimed is:
1. Apparatus comprising
(a) a reflecting means,
(b) a first lens;
(c) a second lens;
(d) a block with a passage at least partially therethrough with
said second lens being at least partially supported by said block
in a position at least partially over one end of said passage and
said reflecting means being positioned in said passage;
(e) a superstructure mounted on said block;
(f) a tubular member having a first end and a second end with said
first lens being mounted adjacent the second end of said tubular
member, the interior of said tubular member being adapted for
receiving a fiber optic probe;
(g) a slidable mounting means affixed to said superstructure
slidably mounted said tubular member adjacent said superstructure,
said first lens, said second lens and said reflecting means being
in alignment so that a beam of light emitted from a fiber optic
probe when received by the interior of the tubular member passes
through the first lens, the second lens and is reflected by the
reflecting means back through the second lens and the first lens,
in that order, to the fiber optic probe, and wherein said first
lens at least partially protrudes from adjacent said tubular member
toward said second lens and said second lens at least partially
protrudes from said block towards said first lens;
(h) a sample area having at least one dimension fixed by the
distance between said first lens and said second lens; and
(i) squeezing means suitable for squeezing a sample positioned in
the sample area between the first lens and the second lens to a
predetermined thickness.
2. Apparatus as in claim 1 wherein said squeezing means
comprises:
(a) an annular flange affixed to said tubular member intermediate
the first and second ends thereof and adapted to abut against said
slidable mounting means; and
(b) draw-down means cooperating with said annular flange and said
slidable mounting means to draw said annular flange down into
contact with said slidable mounting means.
3. Apparatus as in claim 2 wherein said slidable mounting means is
adjustable with respect to said superstructure.
4. Apparatus as in claim 3 wherein: said reflecting means comprises
a concave spherical mirror.
5. A method for taking optical measurements of a semi-solid
material comprising:
(a) placing a sample of material into contact with a first
protruding lens;
(b) moving a second protruding lens into contact with the
sample;
(c) squeezing a portion of the sample to a predetermined thickness
between the first lens and the second lens by moving the second
lens;
(d) providing a primary beam of electromagnetic radiation normal to
said lens;
(e) transmitting at least part of the primary beam through the
first lens, the sample portion and the second lens;
(f) reflecting at least part of the transmitted primary beam back
through the second lens, the sample portion and the first lens in
that order; and
(d) comparing a property of the reflected beam to a property of the
primary beam.
6. A method as in claim 5 wherein the sample is squeezed to a
predetermined thickness of between about 0.5 and about 5
millimeters.
7. Apparatus comprising
(a) a reflecting means,
(b) a first lens;
(c) a second lens;
(d) a block with a passage at least partially therethrough with
said second lens being at least partially supported by said block
in a position at least partially over one end of said passage and
said reflecting means being positioned in said passage;
(e) a superstructure mounted on said block;
(f) a tubular member having a first end and a second end with said
first lens being mounted adjacent the second end of said tubular
member, the interior of said tubular member being adapted for
receiving a fiber optic probe;
(g) a slidable mounting means affixed to said superstructure
slidably mounting said tubular member adjacent said superstructure,
said first lens, said second lens and said reflecting means being
in alignment so that a beam of light emitted from a fiber optic
probe when received by the interior of the tubular member passes
through the first lens, the second lens and is reflected by the
reflecting means back through the second lens and the first lens,
in that order, to the fiber optic probe;
(h) a sample area having at least one dimension fixed by the
distance between said first lens and said second lens; and
(i) squeezing means suitable for squeezing a sample positioned in
the sample area between the first lens and the second lens to a
predetermined thickness.
Description
BACKGROUND OF THE INVENTION
The invention relates to an apparatus for forming and containing
semi-solid samples of reproducible thickness for the performing of
optical measurements thereon. In another aspect, the invention
relates to a method for taking optical measurements of a semi-solid
sample.
In colorimetric and spectrophotometric studies, sample containers
are required for holding the samples to be studied. The sample
containers provided by the prior art were not well adapted for the
study of semi-solid samples which include, for example, gels,
amorphous polymers, and highly viscous liquids. Semi-solid samples
do not flow as readily as the liquids for which the cells provided
by the prior art were designed. Because of this, it was difficult
to force semi-solid samples to fit into the contours of prior art
cells to obtain reproducible sample dimensions. It has thus been
difficult to obtain samples of semi-solid materials having
reproducible thickness by utilizing the sample cells of the prior
art. Difficulties were also encountered in obtaining bubble-free
samples, and also in cleaning the sample cells after use. For
quantitative studies of the optical properties of semi-solid
materials, it is thus extremely desirable to have an easy-to-clean
apparatus for producing bubble-free semi-solid samples of
reproducible thicknesses.
OBJECTS OF THE INVENTION
It is thus an object of this invention to provide a sample cell
suitable for use with semi-solid samples which produces bubble-free
specimens of reproducible thickness.
It is a further object of this invention to provide a sample cell
suitable for use in studying colorimetric and spectrophotometric
properties of semi-solid samples.
It is another object of this invention to provide a sample cell for
use with semi-solid samples which is simple and requires little
maintenance.
It is yet another object of this invention to provide a method for
taking optical measurements of semi-solid materials.
SUMMARY OF THE INVENTION
According to the invention, a sample cell comprises two lenses with
a sample area therebetween with at least one of the lenses being
movable with respect to the other so that a semi-solid sample may
be placed in the sample area and squeezed to a predetermined
thickness. Further according to the invention, optical measurements
of a semi-solid sample are taken employing the above-described
sample cell by transmitting electromagnetic radiation, such as
light, from a source through the first lens, the semi-solid sample
of predetermined thickness, and the second lens; reflecting the
light thus transmitted back through the second lens, the semi-solid
sample of predetermined thickness, and the first lens; receiving at
least a portion of the light back at a receiving means; and
comparing the light transmitted from the source to the light
received by the receiving means.
BRIEF DESCRIPTION OF THE DRAWING
FIG. 1 is a perspective view of a sample cell in accordance with
one embodiment of the present invention with part of the housing
broken away.
FIG. 2 is an exploded view of the sample cell of FIG. 1.
FIG. 3 is a cross-sectional view of the sample cell of FIG. 1.
DETAILED DESCRIPTION OF THE INVENTION
In FIG. 1 the reference numeral 10 designates generally the sample
cell of the present invention. The reference numeral 12 designates
generally a fiber optic probe suitable for use with the present
invention.
The apparatus 10 comprises a lens 14 and a lens 16. The lenses 14
and 16 are constructed of a material which is relatively
transparent to radiation being utilized in study of a semi-solid
material. The lenses can be constructed of any suitable material,
such as for example glass, silica or quartz. Preferably, the lenses
are flat discs and are identical but they can be of different sizes
and shape. The lens 14 and the lens 16 partially define a sample
area 18 which, as illustrated in FIG. 3, is at least partially
occupied by a sample 20. Lens 16 partially rests on suitable
support means such as a block 22. Preferably, the lens 16 is
cemented in place in a recess in an upper surface of the block 22
with at least a portion of the lens 16 protruding above the surface
of the block 22 toward the lens 14. The block 22 has a passage 24
extending at least partially therethrough and in contact with the
lens 16. Passage 24 is defined by an interior surface 26 of the
block 22. Reflecting means, such as a mirror 28, is mounted in the
passage 24 at a distance from the lens 16 by any suitable mounting
means. As illustrated, the mirror 28 rests in a mirror support
means which rests on a cap 32. The cap 32 is threadably retained to
a portion of the interior surface 26 of the block 22.
The mirror support means is preferably constructed of steel or
brass and comprises a tubular member 29 with an annular flange
partially closing the upper end. The tubular member 29 has a
partially threaded interior surface defining a bore and an outside
diameter allowing it to be closely received in passage 24. The
mirror 28 is located within the tubular member 29 and extends at
least partially across the bore of the tubular member 29. The
mirror 28 faces toward the annular flange of tubular member 29.
Biasing means, such as spring 30 are located between the mirror 28
and the annular flange. The spring 30 cooperates with the annular
flange and the mirror 28 to urge the mirror 28 toward a mirror
support ring 31. The mirror support ring 31 has a threaded exterior
surface in engagement with the threaded interior surface of tubular
member 29. The mirror support ring 31 is thus threadably adjustable
within the tubular member 29. Mirror aiming means, such as the
screws 34 establish cooperation between the mirror support ring 31
and the mirror 28. There are preferably three screws 34, so as to
provide three points of cooperation between mirror support ring 31
and the mirror 28. Each screw 34 has a headed end and a tip end.
The mirror 28 is urged against the tip ends of the screws by the
spring 30. The screws 34 extend normally through the body of the
mirror support ring 31 in threaded bores. By adjustment of the
screws 34 in the threaded bores through the mirror support ring,
the mirror 28 can be aimed.
The lens 14 is supported by suitable support means at a distance
from the lens 16. The distance between the lenses fixes at least
one dimension of the sample area 18. As illustrated, the lens 14
support means comprises a tubular member 38 having a first and a
second end slidbably mounted adjacent a superstructure 46. The
superstructure 46 and the tubular member 38 are preferably
constructed of aluminum. The superstructure 46 is mounted to the
block 22 by any suitable means, such as by screws 47. The lens 14
is mounted adjacent the second end of the tubular member 38,
preferably in a recess and at least partially protruding from the
recess toward the lens 16. The lens 14 can be secured in the recess
by any suitable means, such as by cementing using optical cement.
An interior surface of the tubular member 38 defines a bore 50
suitable for receiving the fiber optic probe 12 which is attached
to a colorimeter or the like (not shown) via an optical fiber cable
52. Preferably, the superstructure 46 forms an open ended housing
around the lens 14 and the lens 16.
Slidable mounting means, such as a bushing 40, slidably mounts the
tubular member 38 to the superstructure 46. Together, the block 22,
the superstructure 46, the bushing 40, and the tubular member 38
cooperate to function as a support means to position lens 16
between lens 14 and mirror 28, and to align lens 14, lens 16 and
mirror 28 so that a beam of light passing through the lenses is
reflected back through the lenses by mirror 28. The bushing 40 is
preferably constructed of steel or brass. The bushing 40 is
adjustable with respect to superstructure 46 due to its being
threadably mounted to the superstructure 46. A lock nut 48 prevents
unintentional movement between the bushing 40 and the
superstructure 46. The lock nut 48 is preferably constructed of
steel or brass. An annular flange 42 mounted intermediate the ends
of the tubular member 38 acts to hold the lens 14 a predetermined
distance from the lens 16 by abutting against an upper portion of
bushing 40. Preferably, the annular flange 42 is integral with the
tubular member 38 and is constructed of aluminum. Suitable
draw-down means, such as a draw-down nut 44, urge and hold the
flange 42 adjacent the upper end of the bushing 40. Preferably, the
draw-down nut 44 is constructed of steel or brass. Together, the
annular flange 42 and the draw-down nut 44 cooperate to function as
squeezing means for squeezing a sample placed in the sample area
18. Preferably, tubular member 38 and bushing 40 are oriented with
respect to each other by means such as a key and channel
arrangement as is well known to those skilled in the art.
The optical fiber probe 12 comprises a sleeve 54 surrounding a
bundle of optical fibers. The sleeve 54 is adapted for closely
fitting the bore 50 in the tubular member 38. Preferably, sleeve 54
will only fit into bore 50 in one orientation. It can be secured in
the desired orientation by any suitable means such as by cementing
with sealing wax. Preferably, the sleeve 54 is constructed of
stainless steel. About one-half of the optical fibers within sleeve
54 are adapted for transmitting and emitting electromagnetic
radiation and about one-half of the optical fibers are adapted for
receiving and transmitting electromagnetic radiation. A suitable
probe is available from Brinkmann Instruments, Incorporated of
Houston, Texas. The modification comprises merely removing the
factory tip from the probe and replacing it with a tip such as the
sleeve 54. The sleeve 54 can be secured to the bundle of optical
fibers by any suitable means. Preferably, a sealing wax is
utilized.
In operation of the present invention, the draw-down nut 44 is
disengaged from the bushing 40 and the tubular member 38 at least
partially removed from the remainder of the apparatus 10. A sample
of semi-solid material is placed onto the lens 16. The tubular
member is then lowered through the bushing 40 until lens 14 comes
into contact with the sample. The draw-down nut 44 is engaged with
the bushing 40 and tightened, so that the distance between the lens
14 and the lens 16 is reduced and any excess semi-solid sample
squeezed from the sample area 18 between the two lenses. The
distance between the two lenses is precisely controlled by the
contact of the annular flange 42 with the bushing 40. The vertical
positioning of bushing 40 can be adjusted to obtain samples of
whatever thickness is desired. Samples of 0.5 to 5 millimeter thick
are preferred, although thiner or thicker samples can be obtained
if desired.
As the draw-down nut 44 forces the annular flange 42 into contact
with the bushing 40, the sample 20 partially escapes the sample
area 18. Due to the elevated position of the lens 16 with respect
to the support means 22, the escaped portion of sample 20 protrudes
outwardly from sample area 18 or falls downward onto an upper
surface of the support means 22 from which it can be easily
removed. The portion of the sample 20 which remains in the sample
area 18 is sandwiched between the lens 14 and the lens 16 and if
this distance is maintained constant for different samples, each
sample has a uniform thickness. With each sample positioned as
shown for sample 20, a beam of light can be passed through lens 14,
the sample 20 and lens 16 so that the absorptivity of each sample
can be precisely determined.
As described, the fiber optic probe 12 can be inserted into the
tubular member 38 and thus aligned normally to the lens 14, the
sample 20, the lens 16 and the reflecting means 28. A desired
wavelength of electromagnetic radiation is transmitted as a primary
beam through the fiber optic probe 12 and passes through the lens
14, the sample 20, the lens 16 to the reflecting means 28 from
where it is reflected back through the lenses and sample and
received back into the fiber optic probe 12 for transmission to a
detecting means (not shown). By comparison of a property of the
light emitted from the fiber optic probe 12 to a property of the
light received by the fiber optic probe 12, information can be
obtained about the optical characteristics of the sample 20.
Although any type of mirror can be used as the reflecting means 28,
the reflecting means 28 preferably comprises a concave spherical
mirror. Preferably, the distance between the mirror and the sample
will be adjusted relative to the axis of symmetry of the concave
mirror so that the intensity of reflected light reaching the fiber
optic probe 12 is at a maximum. Normally, this maximum will be
achieved when the distance between a portion of the mirror in axial
alignment with the lens 14 and the lens 16 is at a distance from
the sample approximately equal to the radius of curvature of the
mirror. Preferably, the mirror is a front-surfaced silvered
mirror.
It is important to remove any residual sample remaining on the
lenses of the apparatus between experimental runs. This is easily
accomplished by disengaging the draw-down nut 44 from the bushing
40 and at least partially removing the tubular member 38 from the
reaminder of the apparatus. The lenses are then easily reached and
cleaned with a swab dampened with a suitable solvent. Cleaning is
greatly facilitated when the embodiment of the invention employed
utilizes protruding lenses. Methanol is the solvent presently
preferred.
In the use of the cell, standardization can be accomplished by any
suitable means. For example, if the dispersion of carbon black and
a given polymer is being studied, a sample of the polymer
containing no dispersed carbon black can be used as the reference
standard. The sample containing no dispersed carbon black is
squeezed between the lenses 14 and 16 to a desired thickness and
the absorbance of the standard set at 0 or, alternatively,
transmission set at 100 percent. Alternatively, air can be employed
as the reference standard once the relationship between the
absorptivity of air and polymer sample is established.
* * * * *